Continuous casting



Aug. 11, 1964 E. BALL commuous CASTING 4 Sheets-Sheet 1 Filed Oct. 5, 1961 FIG.

Aug. 11, 1964 E. BALL CONTINUOUS CASTING 4 Sheets-Sheet 2 Filed 001,. 5, 1961 24 a2 6/ He. 2.

//v ve/vroe Eric Ba m M, M MW I 14770/2NEX5 Aug. 11, 1964 E. BALL CONTINUOUS CASTING 4 Sheets-Sheet 5 Filed 001;. 5, 1961 Aug. 11, 1964 E. BALL CONTINUOUS CASTING Filed Oct. 5, 1961 4 Sheets-Sheet w, 4 hm Avoews s United States Patent 3,143,776 CONTIPJUGUS CATENG Eric Ball, Walton-on-Thames, Surrey, England, assrgnor to Continuous Casting Company Limited, Surrey, England, a company of Great iiritain Filed (let. 5, 1961, Ser. No. 143,212 Claims priority, application Great Britain Get. 6, 1961 11 Claims. (ill. 22-612) This invention relates to the continuous casting of metal in a vertical continuous casting plant, and is concerned with the provision of improved means for handling sections cut oif from the continuously cast product, for errample a slab, bloom, billet or ingot, as it descends vertically in a continuous length beneath the mould.

With heavy castings it is obviously desirable that a section weighing perhaps several tons severed from the lower end of the newly-cast continuous casting should not be allowed to fall freely through any considerable distance into a receiver, or the resultant impact will certainly damage the casting and/or the plant.

It has already been proposed in this type of plant to employ as the receiver a tilting frame having a movable supporting shoe which is advanced into supporting contact with the lower end of the casting before the severing of a section from the casting has been effected, and is then moved downwardly in controlled synchronism with the descending casting during the severing operation and for short period after severing is complete, so that it suports the entire weight of the severed section; then the descending shoe, carrying the severed section, is accelerated until it approaches the bottom of its travel and is then decelerated to a standstill, the frame with the shoe is tilted until the section is substantially horizontal, and the section is pushed out of the frame onto a conveyor.

According to the present invention, in a method of operating a vertical continuous casting plant having a receiver spaced vertically beneath the mould to receive the severed sections of the casting, during the operation of severing a section a vertically movable buffer foot is held lightly in contact with the lower end of the section without supporting a substantial proportion of the weight of the section, and when severing is complete the severed ection is allowed to fall under gravity pushing the foot down beneath it, without substantial restraint to its free fall until it reaches a predetermined speed, whereafter an upward braking force is applied to the severed section by the foot.

For example, during the severing operation and subsequent free fall of the section, the upward thrust applied by the foot to the lower end of the section may be restricted so that it does not exceed of the weight of the section.

Preferably, when the severed section reaches the predetermined speed the braking force applied by the foot is suflicient to prevent further acceleration of the section, and the latter descends at a constant speed until it approaches the receiver, when it is subjected to an increased braking force by the foot to decelerate it to a suitably slow speed at which it is deposited in the receiver.

The braking force may be applied via the foot by hydraulic dashpot means. Thus the foot may be coupled to a hydraulic ram, the rate of escape of fluid from the ram cylinder being controllable to effect a variable braking of the foot.

The invention according to another of its aspects comprises a vertical continuous casting plant having a receiver spaced vertically below the mould to receive sections severed from a continuous casting descending from the mould, and having a buffer foot constrained to move along a vertical track with the foot projecting beneath the casting, means for severing a section of predetermined length from the lower end of the casting whilst the latter is descending towards the receiver, means for holding the foot lightly in contact with the lower end of the section during the severing operation and during the initial fall of the severed section from the casting when severing is complete, during which period the upward thrust applied by the foot to the section is controlled to a limited value constituting only a minor proportion of the weight of the section, and means for thereafter automatically causing the foot to apply a controlled and increased upward braking force to the severed section after the latter has reached a predetermined speed of fall towards the receiver.

In one arrangement of the invention, the foot is coupled to a hydraulic ram for controlled hydraulic braking thereby, the ram having means for regulating the rate of escape of fluid from the ram cylinder under the load applied to it by the foot.

Preferably the foot is guided for movement along a fixed vertical track independently of the receiver, which may comprise a tiltable basket, the track extending vertically above the highest part of the receiver.

The invention may be carried into practice in various Ways but one specific embodiment will now be described by way of example with reference to the accompanying drawings, in which:

FlGURE l is a sectional side elevation of a vertical continuous casting plant;

FIGURE 2 is a view on an enlarged scale of the lower part of the plant of FIGURE 1 in the vicinity of the downender basket;

FIGURE 3 is a diagram showing the hydraulic control means used for controlling the descent of a severed section of a billet to the downender basket, and

FIGURES 4 and 5 are respectively an elevation and plan view of an enlarged scale showing the swinging rollers associated with the downender basket.

The embodiment illustrated generally in FIGURE 1 comprises a vertical continuous casting plant provided with a mould 10 mounted at the upper end of a supporting framework 11 some feet in height, the usual cooling means being provided for chilling the walls of the mould 19 whilst molten metal is poured into the open upper end of the mould from a ladle 9. A newly cast slab is with drawn vertically downwardly in a continuous length from the open bottom of the mould by means of sets of powerdriven withdrawal rollers 12 and 13 which are mounted on the framework 11 some distance below the mould and which grip the newly cast continuous slab between them. Between the bottom of the mould 10 and the upper withdrawal roller 12 are a number of slab guide rollers 14, and cooling liquid is sprayed onto the descending billet from sets of spray nozzles 15.

Mounted on the framework 11 below the two withdrawal rollers 12 and 13 are vertical guide rails 16 on which travels a burner carriage 17 supporting oXy.-pro-, pane gas burners for cutting off a section of predetermined length from the lower end of the newly cast slab. The burner carriage 17 is provided with hydraulic ram means (not shown) for raising it up to the top of the guide rails 16, and with means for clamping it to the descending slab so that it will be moved down the guide rails with the descending slab to which it is clamped whilst the slab is being severed by the operation of the burners.

A vertical guideway 24) for a vertically movable buflier foot 21 is also mounted on the supporting framework 11 and extends from a level close to the bottom of the plant up to the level of the tops of the guide rails 16 for the burner carriage. The total height of the foot guideway is some 40 feet. As will be described later in connection with FIGURES 2 and 3, the foot 21 is guided for vertical movement along the guideway 20 and protrudes into the path of movement of the decending slab, being formed with a horizontal upper surface for engagement beneath the lower end of the slab. The buffer foot is controlled by hydraulic-powered control means, to be described with reference to FIGURE 3, so that the upward thrust which it applies to the lower end of the slab resting on it can be controlled as the slab descends during the operation of severing a section from it and during the subsequent descent of the severed section.

Mounted at the bottom of the framework 11 is a down ender basket 22 of elongated form pivoted at one end on a fixed pivot shaft 23, which is positioned beneath the mould in a position in which its horizontal pivotal axis is slightly offset from the projected longitudinal axis 24 of the descending slab. The downender basket 22 can be tilted through 90 about the shaft 23 by means of a hydraulic ram 25, the basket 22 being movable between a vertical position as shown in FIGURES l and 2 in which the open upper end of the basket is directly beneath the lower end of the mould 10, and a horizontal position in which it overlies and co-operates with the end section of a horizontal roller conveyor 26. The conveyor 26 leads to an elevator indicated generally at 27 and provided witha vertically movable platform 28 which can be raised by means of cables 29 passing around a system ofpulleys and wound on winches 30 driven by winding motors 31. As indicated, the platform 28 is counterbalanced by a balance weight 32. In its lowermost position the platform 28, which is provided with four horizontal fingers 33, co-operates with the horizontal roller conveyor 26, so that a severed section of slab indicated at 34 can be pushed on to the fingers 33 of the platform 28, which can then be lifted vertically by the winches 30 to a predetermined level at which the slab section 34 is discharged from the platform.

The foot 21 is mounted on a trolley (shown diagrammatically at 36 in FIGURE 3) which is guided for vertical movement along the guideway 20 by means of rollers 37 engaging the guideway. The foot 21 is controlled by means of a pair of hydraulic rams 40 whose rarn piston rods 41 carry pulleys 42 around which passes a flexible cable 43, one end of which is anchored at 44 to a fixed anchorage provided on the framework 11 and the other end of which is secured at 45 (FIGURE 3) to the trolley 36. The cable 43 also passes around a pair of fixed-axis pulleys 46 journalled on the framework 11 above the hydraulic rams 40 at a level just above the top of the guideway 20. Thus the foot 21 and'the trolley 36 can be raised along the guideway 20 by actuation of the hydraulic rams 40 to move their piston rods 41 downwardly together with the movable pulleys 42. Similarly, the descent of the foot 21 under the weight of the slab, and subsequently under the weight of a severed section of the slab, can be controlled by means of the rams 40, by which a controlled braking force can be applied to the foot 21 via the cable and pulley system 42, 43, 46, during the descent of the foot. For this purpose the rams 40 are provided with an electro-hydraulic control system shown diagrammatically in FIGURE 3. In FIGURE 3 only the hydraulic components and connections of the electro-hydraulic system are shown, the electrical circuits and limit switches being omitted for the sake of clarity.

In the hydraulic system illustrated in FIGURE 3, the lower ends of the cylinders of the two hydraulic rams 40 are connected in parallel to a common pressure line 50, whilst their upper or annulus ends are similarly connected in parallel to a second pressure line 51. The lines 50 and 51 are respectively connected to ports 1 and 2 on one side of a control valve V the valve V having on its other side ports 3 and 4 which are respectively connected to a pressure line 52 leading via a normal-speed metering valve V to a low-pressure return channel R common to the system, and via a pressure line 53 to the discharge outlet of a pump P constituting a supply of pressurised hydraulic fluid for the system. The valve V is'a three-positionvalve which when in its centralised position as illustrated cuts off communication completely between the ports 1 and 2 and the ports 3 and 4. When moved towards the left in FIGURE 3 into one open position it connects the port 1 to the port 3 and the port 2 to the port 4, and when moved in the other direction into its other open position it connects the port 1 to the port 4 and the port 2 to the port 3 so as to reverse the connection of the pressure fluid supply and the return to the hydraulic rams. Connected in series with the pressure line 50 is an adjustable pressure-reducing valve V in series with which is a non-return valve N A reservoir of fluid 54 is also connected through a non-return valve N to the pressure line 50 for the purpose of topping up the system. The pressure-reducing valve V and the non-return valve N can be bypassed by means of a bypass line 55 controlled by a bypass valve V of the openshut type. Moreover, the system includes a further metering valve V which when opened connects a point of the pressure line 50 direct to the common return R.

The pressure line 51 that connects the control valve port 1 to the annulus ends of the jack cylinders incorporates an adjustable pressure switch S which is responsive to the pressure in the line 51 and hence to the pressure in the annulus ends of the cylinders 40. The pressure switch closes in response to the attainment of a predetermined level of pressure in the line 51, and when closed energises electric relays by which the control valve V in FIGURE 3 and the normal-speed metering valve V are opened, as will be described. A slow-down metering valve V is connected between the pressure line 52 and the common low-pressure reservoir or return R, and is also relay operated, as are the valves V and V The electric relays which operate the various valves are controlled in accordance with a desired sequence-operated cycle by associated automatic control means of conventional construction, which will not be described in detail herein.

In the general operation of the plant during a casting cycle, the foot 21 is raised initially by means of the hydraulic rams 40 towards the top of the guideway 20 until it comes into contact with the lower end of the newly cast slab which is descending at a speed of perhaps 3 feet per minute from the mould. At this stage, the foot 21 merely rests in light contact with the lower end of the descending slab, and is pushed down thereby against a low frictional and hydraulic resistance so that it will not support more than 5% of the weight of the section to be severed. Thus the hydraulic counter-balancing produced at this stage by the rams 40 under the control of the control system of FIGURE 3 is such that the upward thrust applied by the foot 21 to the bottom of the slab is limited to a required value, which in the case of a 10 ton section would be below 1,000 lbs. The burner carriage 17 at the top of its guide rails 16 is automatically clamped to the slab at a desired level where a cut is required, and the burners come into operation to cut progressively through the descending slab until a section of the desired length is severed. During this severing operation, the foot remains pressed relatively lightly against the bottom of the slab as described above and is pushed down by the descending slab, the thrust between them not exceeding the limiting value referred to above.

As the severing operation is completed, the severed section falls clear of the main length of the slab suspended from the withdrawal rolls 12 and 13, and accelerates downwardly under gravity, pushing down the foot 21 beneath it. During the initial part of the fall of the severed section under gravity, the resistance applied by the foot 21 to the lower end of the falling section still does not exceed the limiting value referred to, as it is desired that the severed section shall accelerate rapidly so as to open up a wide gap between itself and the lower end of the main slab. Accordingly the resistance to the fall of the severed section applied by the foot 21 is kept low by the appropriate control of the rams 40, so that the- (9 maximum upward force applied to the severed section by the foot does not exceed the limiting value referred to above, during this stage of the descent of the section.

When the accelerating severed section reaches a predetermined downward speed of perhaps 15 feet per minute, which it will do after a very brief period of acceleration, the escape of hydraulic fluid from the upper or annulus ends of the hydraulic rams 40 is restricted by the setting of the control system to cause the foot to apply an upward hydraulic braking force to the severed section sufficient to prevent further downward acceleration of the section. The section continues to descend at this uniform maximum speed and enters the open upper end of the downender basket 22, which at this time is in its vertical position as shown in FIGURES l and 2. As the severed section approaches the bottom end of the vertical downender basket 22, it is subjected through the foot 21 to a further hydraulic braking which reduces its speed to about 1 foot per minute, at which low speed it is ultimately deposited without excessive shock on to a receiving plate 60 at the lower end of the downender basket.

The downender basket, with the severed billet section embraced in it, is not tilted over about its pivot 23 to its horizontal position, this tilting action being performed by the hydraulic ram 25 whose piston rod 61 acts on a radial lever arm 62 secured to the downender basket 22. As the basket reaches its horizontal position it deposits the severed section horizontally on to the rollers of the conveyor 26, and a pneumatic pusher (not shown) is operated to push the section out of the basket and along the conveyor for removal by the elevator 27. The basket is then tilted back to its vertical position by the arm 25, and the foot raised in readiness for another severing operation.

In order to ensure that the severed section which has been deposited on the receiver plate 60 in the vertical downender basket shall be swung down to a horizontal position together with the basket 22, and shall not remain unsupported in its vertical position when the basket 22 is swung down, two sets of back rollers 65 are provided to engage behind the section and hold it embraced within the downender basket. However, in order that the foot and its trolley shall be free to descend vertically to a position below the receiver plate 66 so as to deposit the section thereon with the downender basket vertical, it is necessary that the back rollers 65 should be swung out of the way of the descending foot and subsequently swung back into engagement behind the section after the foot has decended below them. For this purpose, as shown in detail in FIGURES 4 and 5, the roller 65 of each set is mounted on the outer end of an arm 66 extending radially from one end of a rotatable shaft 67 journalled in bearings 68 mounted on a bedplate 70 which is secured to the frame 11, the axis of the shaft 67 being horizontal. The shaft 67 can be rotated through approximately 90 by means of a hydraulic jack 71 whose piston rod 72 is pivoted to a radial lug 73 protruding from the shaft 67, the actuation of the jack 71 serving to swing the roller 65 into or out of its position of engagement behind the severed section. In FIGURE the projected centreline of the slab is indicated as before at 24 and the outline of the severed section is shown in chain lines at 74. Moreover, to accommodate slabs of different transverse dimensions, the shaft 67 is adjnstably mounted in its bearings 68 so that it can be moved in the axial direction for varying the position of the plane of the swinging roller 65.

The electro-hydraulic control system illustrated in FIGURE 3 operates as follows during the normal cycle of severing a slab section and handling the severed section. Initially the foot 21 is raised to a predetermined level at the top of the guideway 20, where it waits until the leading end of the descending, unsevered slab makes contact with it. When the foot has been raised to this predetermined level the main control valve V and the other valves of the hydraulic system are closed so that no flow of hydraulic fluid into or out of either end of the hydraulic rams 40 is permitted.

When the lower end of the descending slab contacts the buffer foot 21 and attempts to force it downwardly, pressure is built up in the hydraulic fluid in the upper, annulus ends of the cylinders of the rams 4t) and in the pressure line 51, and this pressure acts on the pressure switch S When the pressure in the cylinders 49 reaches a predetermined value corresponding to a thrust of the required limiting value between the bottom of the slab and the foot 21, the pressure in the line 51 will operate the pressure switch S to cause it to energise the relays associated with the valves V and V and thereby to move the valve member V towards the left in FIGURE 3, and also to open V The movement of the control valve V to its left-hand position interconnects the ports 1 and 3 and also interconnects the ports 2 and 4, thereby allowing hydraulic pressure fluid from the pump P to flow through the pressure-reducing valve V and the non-return valve N into the lower ends of the ram cylinders 40, and at the same time allowing fluid to escape from the upper, annulus ends of the ram cylinders and to be discharged through the metering valve V to the low-pressure return R. The reducing valve V is set so that the pressure established in the lower ends of the hydraulic ram cylinders 40 will counterbalance the pulley system hydraulically to an extent sufiicient to overcome friction, so that a small force applied by the descending slab to the foot 21 will produce downward movement of the foot along the guideway and corresponding upward movement of the ram piston rods 41. During this downward movement of the foot the operation of severance of a section of predetermined length from the lower end of the slab by the flame cutters is continuing, and prior to the conclusion of severance the foot will be pushed down by the descending slab at the speed of descent of the latter which corresponds to the casting speed. During this time hydraulic fluid displaced from the annulus ends of the ram cylinders will continue to flow through the ports 1 and 3 of the valve V and through the normal speed metering valve V to the return R. The flow control setting of the metering valve V is such as to permit arate of movement of the foot 21 greatly in excess of the maximum casting speed, so that no significant additional resistance to the downward movement of the foot will be produced by the flow of fluid through V When the severance of the slab section is completed, the severed section will no longer be supported by the length of slab above it and the severed section and the foot will accelerate under gravity until a speed equivalent to the maximum permissible flow rate of fluid through the metering valve V is reached. The further descent of the foot is now controlled to this speed by the restriction afforded by V to the discharge of fluid from the rams 40, until the severed section reaches a level within a few inches of the bottom of the downender basket 22. At this point a limit switch is tripped to open the slow-down metering valve V and to close the normal-speed metering valve V The flow of discharged fluid from the rams 46 is now diverted through the slow-down metering valve V whose setting is such as to restrict further the discharge of fluid from the rams 4t} and thereby to apply hydraulically an upward braking force to the foot 21 and to the severed section resting on it, which reduces the rate of descent of the foot and the section until ultimately the section makes contact with the receiver plate 69 in the bottom of the downender basket 22. At this stage a limit switch is operated automatically to open the bypass control valve V and permit the admission of full hydraulic pressure from the pump P to the lower ends of the ram cylinders 49 below their pistons, thereby moving the foot 21 downwardly a few inches further to clear the downender basket. V is then automatically closed, and the main control valve V is also moved automatically to its closed position so that all ports are shut, thereby preventing any further movement of the foot 21. Simultane- 7 ously, hydraulic pressure from the pump P is automatically applied to the jacks 71 of the back rollers 65 of the downender basket 22 to swing the latter into position behind the severed section resting in the basket, and pressure is then applied to the hydraulic ram 25 of the basket itself to cause the basket, together with the severed section embraced in it, to be tilted over from the vertical to the horizontal position in which the severed section rests on the conveyor rollers. The hydraulic or pneumatic pusher referred to above is then operated to push the section clear of the basket 22 and along the conveyor.

When the severed section is clear of the basket the latter is returned by the ram 25 to its vertical position. When the basket is vertical the control valve V is operated to move the valve member to the right-hand position of FIGURE 3 connecting the port 4 to the port 1 and blocking the ports 2 and 3, and simultaneously the metering valve V is opened. The interconnection of the ports 4 and 1 of the control valve V applies full hydraulic pressure to the upper, annulus ends of the ram cylinders 40 so as to raise the foot 21, the speed of ascent being controlled by the setting of the metering valve V through which the oil displaced from the ram cylinders is passed to return. When the foot reaches its predetermined upper level, a limit switch operates to move the main control valve V to its closed position blocking all ports, and also closes the metering valve V In this condition the various valves are set so that no flow of fluid in the system is permitted, and the mechanism is ready for a subsequent cycle of operations.

It will be appreciated that it is an essential feature of the arrangement described that during the whole of the operation of severing the section of slab, and during the initial fall of the severed section, the buffer foot does not support a significant part of the weight of the section, and that accordingly the acceleration of the section will be both rapid and rapidly initiated once severing is completed, so that a gap will be established as quickly as possible between the top of the severed section and the bottom of the main slab.

It will also be appreciated that the buffer foot 21 does not constitute a part of the downender basket 22, but is mounted quite separately from the latter in its own guideway on the supporting framework. This allows the foot to have a much greater vertical travel than would otherwise be the case, and facilitates the establishment of a wide gap between the top of a severed section in the basket and the bottom of the slab descending from the mould.

In the embodiment described and illustrated the buffer foot may be employed to perform two other functions. Firstly, it may be used under certain circumstances to measure the length of section tobe cut off the slab. This applies particularly when clearing the material left in the machine at the end of the cast. Secondly, the foot can be used when setting up the machine prior to a cast, for lifting a dummy bar out of the downender basket and inserting it between the withdrawal rolls 11 and 12 which feed it up into the lower end of the mould to close the mould prior to the casting of liquid metal in it. In other words the foot is then used to operate the casting machine in reverse.

For controlling the foot to raise it for the purpose of clearing material left in the machine at the end of a cast, the control valve V is moved to its right-hand position in which the ports 1 and 4 are interconnected and the ports 2 and 3 are closed, and the metering valve V is opened. This allows hydraulic fluid to flow under pressure to the upper, annulus ends of the hydraulic ram cylinders 40 to raise the foot, and displaced oil from the lower or piston ends of the cylinders 40 flows through the metering valve 6 to return R. When the foot comes into contact with the bottom of the slab, pressure is built up in the upper, annulus ends of the two ram cylinders 40 and when this reaches a predetermined value it operates the pressure switch S which in turn operates the control valve V to move it to its left-hand position in which the pressure connections to the cylinders are again reversed, theport 4 being connected to the port 2 and the port 3 to the port 1. The operation of the pressure switch also closes the metering valve V The descending slab constituting the residue of the charge now pushes the foot down before it, and the displaced hydraulic'fiuid from the rams 40 is forced through the normal-speed metering valve V to brake the foot as previously described.

The control of the foot for the feeding of a dummy bar into the bottom of the mould is performed as follows. To lower the foot to the bottom of the downender basket, the control valve V is moved into its lefthand position to connect the port 4 to the port 2 and the port 1 to the port 3, and the pormal-speed metering valve V and the bypass valve V are both opened. Fluid pressure is applied to the lower ends of the ram cylinders 40 via the ports 4 and 2 of the valve V and via the open bypass valve'V and raises the piston rods 41 to lower the foot, the displaced fluid from the annulus ends of the ram cylinders 40 passing through the ports 1 and 3 of the valve V andthe metering valve V to regulate the rate of descent of the foot.

To raise the foot again after a dummy bar has been positioned on it in the basket 22, the control valve V is moved to its right-hand position to connect the port 4 to the port 1, and to block the other two ports, and the metering valve V is opened. The pressure switch S is rendered inoperative and therefore full hydraulic pressure is applied to the annulus ends of the ram cylinders 40, andso raises the foot 21 with the dummy slab on it, the displaced fluid from the lower ends of the cylinders 40 escaping through the open metering valve V What I claim as my invention and resire to secure by Letters Patent is:

1. A method of operating a vertical continuous casting plant having a receiver spaced vertically below the mould to receive severed sections of the casting, which comprises severing a section from the lower end of the casting whilst holding a vertically-movable buffer foot lightly in contact with the lower end of the section, and after severmg is complete allowing the severed section to accelerate substantially freely under gravity pushing the foot downwardly beneath it without substantial restraint to the descent of the section until it reaches a predetermined speed, and'thereupon causing the foot to apply a substantial upward braking force greater than the said light contacting force to the severed section.

V 2. method as claimed in claim 1 in which during the severing operation and subsequent free fall of the sectron to the said predetermined speed the upward thrust applied by the foot to the lower end of the section is controlled so that it does not exceed a value equal to 5% of the weight of the section.

3. A method as claimed in claim 1 in which after the severed section has reached the said predetermined speed it is caused to descend at constant speed towards the receiver by controlling the braking force applied by the foot to a Value sufiicient to prevent downward acceleration of the section, and in which when the section approaches the bottom of the receiver it is decelerated to a slower speed by the application to it of an increased braking force by the foot, at which slower speed it is deposited in the receiver.

4. A method as claimed in claim 3 in which the control of the movement of the foot and of the upward thrust applied by it to the section is effected by hydraulic ram means coupled to said foot, the fluid flow in said ram means being controlled by an electro-hydraulic control system.

5. A method as claimed in claim 4 in which the upward force applied by the foot to the bottom of the section is controlled by regulating the rate of escape of hydraulic fluid from the ram cylinder means.

6. A vertical continuous casting plant having an openended vertical-axis mould and a receiver spaced vertically below the mould to receive sections severed from a continuous casting descending from the mould, and having a supporting foot projecting beneath the casting and constrained to move along a vertical path, means for severing a section of predetermined length from the lower end of the casting whilst the latter is descending towards the receiver, means for holding the foot in contact with the lower end of said section, and means for controlling the upward thrust applied by the foot to the lower end of the section, the said control means being arranged to hold the foot only lightly in contact with the section so that the foot does not support more than a minor proportion of the weight of the section during the severing operation and during the initial period of fall of the section after severance up to a predetermined speed of fall, and thereafter to cause the foot to apply an increased upward braking force to the section sufiicient to prevent further downward acceleration of the section after it has reached the said predetermined speed.

7. Apparatus as claimed in claim 6 in which the said control means comprises hydraulic ram means coupled to the foot and an electrohydraulic control system arranged to control the actuation of the ram means, the system including means for regulating the rate of escape of fluid from the cylinder of the ram means under the load applied to the said ram means by the foot,

8. Apparatus as claimed in claim 7 in which the foot is guided for movement along a fixed vertical track independently of the receiver, the track extending vertically above the highest part of the receiver.

9. Apparatus as claimed in claim 8 in which the receiver comprises an elongated basket pivotally mounted to tilt about a horizontal axis near one end, and which includes means for tilting the basket.

10. Apparatus as claimed in claim 9 in which the basket has an open longitudinal side adjacent said track and carries at least one roller mounted to swing between positions in which it extends across said open longitudinal side, and a position in which it is clear of said open side.

11. Apparatus as claimed in claim 6, in which the control means comprises hydraulic ram means connected to the foot, valve means regulating the escape of hydraulic fluid from the ram means, and switch means operatively associated with the said foot to be actuated when the foot reaches a predetermined position close to the lower end of its travel, the switch means being operatively connected to the valve means to increase the upward force applied by the foot and hence decelerate the casting, when the foot reaches the predetermined position.

References Cited in the file of this patent UNITED STATES PATENTS 2,351,962 Harrison June 20, 1944 2,582,329 Harter Jan. 15, 1952 2,806,263 Hogan Sept. 17, 1957 2,898,650 Fredriksson Aug. 11, 1959 3,066,364 Baier Dec. 4, 1962 3,098,269 Baier July 23, 1963 

1. A METHOD OF OPERATING A VERTICAL CONTINUOUS CASTING PLANT HAVING A RECEIVER SPACED VERTICALLY BELOW THE MOULD TO RECEIVE SEVERED SECTIONS OF THE CASTING, WHICH COMPRISES SEVERING A SECTION FROM THE LOWER END OF THE CASTING WHILST HOLDING A VERTICALLY-MOVABLE BUFFER FOOT LIGHTLY IN CONTACT WITH THE LOWER END OF THE SECTION, AND AFTER SEVERING IS COMPLETE ALLOWING THE SEVERED SECTION TO ACCELERATE SUBSTANTIALLY FREELY UNDER GRAVITY PUSHING THE FOOT DOWN- 